Plasticity: capacity to change physiologically in response to environmental stress. Can be: physical environment (temp, exposure to sun, etc. ) cultural environment (available food, etc. ) Flexibility to adapt humans have some capacity to adapt. Homeostasis: a condition of balance in a biological system dynamic steady state. Irreversible eg. volume of lungs, shape of organs (physical response to environment once you stop growing these changes are permanent) Acclimatization: longer term change during lifetime (eg. athlete competing at higher altitudes may go to the place early to adjust to the air pressure etc. Will go back to the way things were when they leave again) Generally smaller animals lose more body heat: allen"s rule: More linear shape = lose more heat: limb proportion and climate: Cold climate: mammals have short limbs and stocky bodies. Hot climate (close to equator): mammals have long, slender limbs and linear bodies. Capillaries at skin"s surface widen to allow increased blood flow lose.